Marine data acquisition node

ABSTRACT

Disclosed are systems and methods for marine geophysical surveying. An example system an electromagnetic source configured to emit an energy field into a body of water; a marine data acquisition node comprising: a base having a buoyancy such that the base is configured to float in a body of water; a geophysical sensor coupled to the base; a weight configured to anchor the marine data acquisition node to a water bottom; and a line connected between the weight and the base configured to prevent the base from floating to a surface of the body of water.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/281,846, filed Sep. 30, 2016, which claims the benefit ofU.S. Provisional Application No. 62/243,214, filed Oct. 19, 2015 theentire disclosures of which are incorporated herein by reference.

BACKGROUND

Techniques for marine geophysical surveying include seismic surveyingand electromagnetic surveying, in which geophysical data may becollected from below the Earth's surface. Marine geophysical surveyinghas applications in mineral and energy exploration and production andmay be used to help identify locations of hydrocarbon-bearingformations. Certain types of marine geophysical surveying, includingseismic and electromagnetic surveying, may include using a survey vesselto tow an energy source at selected depths—typically above theseafloor—in a body of water. The energy source can emit energy, forexample, seismic or electromagnetic energy, into the body of water thatinteracts with subterranean formations below the water bottom. Sensorsmay be used to detect changes in the energy field due to the interactionwith the subterranean formation and generate response signals that canbe used to infer certain properties of the subsurface formation, such asstructure, mineral composition and fluid content, thereby providinginformation useful in the recovery of hydrocarbons.

In conventional systems, the sensors may be located in marine dataacquisition nodes positioned directly on the water bottom. However,positioning the marine data acquisition node directly on the waterbottom may have disadvantages. One such disadvantage may be that theacquired geophysical data may be affected by local variations ofresistivity and/or acoustic impedance. For example, stones, bottomstructures, and/or varying bathymetry may cause local variations ofresistivity and/or acoustic impedance. Another disadvantage that mayarise for marine data acquisition nodes positioned directly on theseafloor may be the housing containing the electrodes used for recordingan electromagnetic field. The housing and electrodes may protrude fromthe marine data acquisition node and may bend, for example, due tounsuitable positioning of the marine data acquisition node, which mayproduce errors in the acquired geophysical data. Yet, anotherdisadvantage that may arise for marine data acquisition nodes positioneddirectly on the seafloor may be that an acquisition node may get stuckin a bottom structure and/or among stones, which may affect the measuredgeophysical data.

BRIEF DESCRIPTION OF THE DRAWINGS

These drawings illustrate certain aspects of systems and methods of thepresent disclosure and should not be used to limit or define the systemsand methods.

FIG. 1 is a schematic illustration of a marine data acquisition nodeanchored to the water bottom, in accordance with example embodiments.

FIGS. 2A-2C are schematic illustrations of a marine data acquisitionnode utilizing multiple weights, in accordance with example embodiments.

FIG. 3 is a schematic illustration of multiple marine data acquisitionnodes attached together, in accordance with example embodiments.

FIG. 4 is a schematic illustration of a geophysical survey systemcomprising marine data acquisition nodes, in accordance with exampleembodiments.

DETAILED DESCRIPTION

This disclosure is related generally to the field of marine geophysicalsurveying. Marine geophysical surveying may include, for example,seismic and/or electromagnetic surveying, among others, in whichgeophysical data may be collected regarding subsurface formations.

In some embodiments, a marine data acquisition node may be provided thatcomprises a base and a geophysical sensor coupled to the base. Inaccordance with example embodiments, the base of the marine dataacquisition node may be positioned near the bottom of a body of water,such as, for example, a water bottom. However, the base of the marinedata acquisition node may not be positioned directly on the waterbottom. In contrast to some currently used approaches in which themarine data acquisition node may be positioned directly on the waterbottom, the base of the marine data acquisition node may have a buoyancysuch that the base may float a certain distance above the water bottom.By way of example, embodiments may further include a weight coupled to aline of a certain length. Without limitation, the line may couple theweight to the base. In operation, the weight may be positioned on thebottom of the body of water such that the base of the marine dataacquisition node floats a certain distance above the water bottom.

Although the following discussion relates to a first marine dataacquisition node 100, it should be understood that it also equallyapplies to a second marine data acquisition node 200, as the firstmarine data acquisition node 100 is substantially identical to thesecond marine data acquisition node 200 of the present disclosure.Further, marine data acquisition nodes in addition to second marine dataacquisition node 200 may also be substantially identical to first andsecond marine data acquisition nodes 100, 200. In some embodiments,marine data acquisition node 100 may be used with a dissimilar marinedata acquisition node.

A marine data acquisition node may comprise a base having a buoyancysuch that the base is configured to float in a body of water; ageophysical sensor coupled to the base; a weight configured to anchorthe base to a water bottom; and a line connected between the weight andthe base configured to prevent the base from floating to a surface ofthe body of water.

A marine electromagnetic survey method may comprise deploying a marinedata acquisition node in a body of water, wherein the marine dataacquisition node may comprise a base having a buoyancy such that thebase floats in the body of water; a geophysical sensor coupled to thebase; a weight that anchors the marine data acquisition node to a waterbottom; and a line connected between the weight and the base thatprevents the base from floating to a surface of the body of water; andemitting an energy field into the body of water. The method may furthercomprise detecting changes in the energy field with the marine dataacquisition node due to an interaction with a subterranean formation.

A method of manufacturing a geophysical data product may comprisedeploying a marine data acquisition node in a body of water, wherein themarine data acquisition node comprises: a base having a buoyancy tofloat in the body of water; a geophysical sensor coupled to the base; aweight that anchors the marine data acquisition node to a water bottom;and a line. The method may further comprise emitting an energy fieldinto the body of water. The method may further comprise measuring one ormore components of the energy field with the marine data acquisitionnode. The method may further comprise recording the measurements madewith marine data acquisition node on one or more non-transitory computerreadable media, thereby creating the geophysical data product.

An electromagnetic survey system may comprise an electromagnetic sourceconfigured to emit an energy field into a body of water; a marine dataacquisition node comprising a base having a buoyancy such that the baseis configured to float in the body of water; a geophysical sensorcoupled to the base; a weight configured to anchor the base to a waterbottom; and a line connected between the weight and the base configuredto prevent the base from floating to a surface in the body of water.

FIG. 1 illustrates a marine data acquisition node, such as first marinedata acquisition node 100, in accordance with example embodiments. Asillustrated, first marine data acquisition node 100 may be configured todeploy in body of water 170. First marine data acquisition node 100 mayinclude a base 101. The base may have a buoyancy such that the base 101floats in the body of water 170. In some embodiments, the base 101 mayinclude at least one arm, such as, for example, arms 102, 104, 106 and108. The base 101 may be of a three-dimensional shape, including, butnot limited to, a cylinder, a cone, a sphere, a cube, a pyramid, aprism, or any combination thereof. Base 101 may include a hollowinterior chamber. Base 101 may also include a lateral surface area, forexample, lateral faces. Without limitation, the base 101 may beconstructed, for example, from a rigid, high strength, high densityplastic or another rigid, high strength material suitable for subseadeployment. Base 101 may also be constructed from metal which may betotally isolated from any electronics. Where base 101 is utilized as anelectrode, the surface (outer layer) of the base 101 may be constructedfrom a material suitable for use as an electrode, such as Ag/AgCl (whicha person of ordinary skill would recognize as silver-silver chloride),whereas, an inner layer (main material) of the base 101 may beconstructed from, for example, titanium, stainless steel or any othernon-corrosive alloy with sufficient strength to withstand pressure atvarious depths in a body of water. Additionally, the base 101 may beconstructed from an electrically non-conducting material.

In some embodiments, the base 101 may include sensor electronics 110disposed within base 101. The sensor electronics 110 may include a widevariety of devices (none shown separately) for operating the firstmarine data acquisition node 100. The sensor electronics 110 mayinclude, for example, electronics for sampling and logging thegeophysical data sensed by the receiver electrodes 114, 116, 118, and120. The sensor electronics 110 may also include recording electronics,control electronics, and/or data storage associated with the receiverelectrodes 114, 116, 118, and 120. For example, the sensor electronics110 may include electronic memory and/or a signal processor.Additionally, the sensor electronics 110 may further include amagnetometer, a tilt sensor, and/or a battery. To conserve battery life,the sensor electronics 110 may be turned on at deployment or in the bodyof water 170, for example.

In some embodiments, sensor electronics 110 may further include anacoustic location system. The acoustic location system may include anyof a variety of devices (none shown separately) for generating acousticsignals that may be used to determine the location of first marine dataacquisition node 100. The acoustic location system may include, forexample, an acoustic responder and/or a compass to determine orientationand approximate direction of the first marine data acquisition node 100.

In some embodiments, first marine data acquisition node 100 may furtherinclude a geophysical sensor, such as, for example, receiver electrodes114, 116, 118, and 120. The geophysical sensors may be operable togenerate a signal that is related to a parameter being measured by thegeophysical sensor. The geophysical sensors may be any type ofgeophysical sensor known in the art, including seismic sensors, such ashydrophones, geophones, particle velocity sensors, particle displacementsensors, particle acceleration sensors, or pressure gradient sensors, orelectromagnetic field sensors, such as electrodes (e.g., receiverelectrodes 114, 116, 118, and 120) or magnetometers. While FIG. 1illustrates use of arms 102, 104, 106, 108 for supporting andpositioning receiver electrodes 114, 116, 118, and 120, it should beunderstood that arms 102, 104, 106, 108 may not be required and thatgeophysical sensors may be disposed on base 101, for example, withoutuse of arms 102, 104, 106, 108. In operation, the geophysical sensorsmay detect energy that originated from an energy source (e.g., energysource 174 on FIG. 4) after it has interacted with subterraneanformations 182 beneath the water bottom 180. By way of example, thegeophysical sensors may generate signals, such as electrical or opticalsignals, in response to the detected energy. The detected energy may beused to infer certain properties of the subsurface rock, such asstructure, mineral composition and fluid content, thereby providinginformation useful in the recovery of hydrocarbons.

In some embodiments, base 101 may further include a buoyant material 112coupled to the base 101. The buoyant material 112 may provide thebuoyancy to the base 101 such that the base floats in the body of water170. As illustrated, the buoyant material 112 may be disposed within thebase 101. The buoyant material 112 may substantially fill the hollowinterior chamber of base 101. However, while FIG. 1 illustrates thebuoyant material 112 disposed within the base 101, embodiments mayinclude other configurations for coupling the buoyant material 112 tothe base 101, for example, the buoyant material 112 may be secured abovethe base 101 (e.g., with a line) providing buoyancy for the base 101 tofloat. Without limitation, the buoyant material 112 may add buoyancy sothat the base 101 of first marine data acquisition node 100 may float acertain distance above water bottom 180. Additionally, buoyant material112 may allow flotation to the surface for recovery when surveying iscomplete. Additionally, the buoyant material 112 may also exclude fluid(e.g., water) from the hollow interior chamber of base 101 and/orelectrically insulate the various components inside base 101. A widevariety of materials may be used as the buoyant material 112, includinga curable, synthetic urethane-based polymer or other gel-like substancethat can be used to fill the hollow interior chamber of base 101.Additional materials that may be used for the buoyant material 112include, without limitation, glass spheres, which may be mixed in anepoxy resin, for example.

In some embodiments, base 101 may further be ballasted, for example, byinclusion of a ballast material (not shown) disposed within the base101. Base 101 may include a large air-filled cavity that may providebuoyancy and a ballasting weight (or thicker wall material) on thebottom of base 101 for the purpose of aligning the base 101. Base 101may also include a compact non-buoyant electronics housing, a ballastmaterial, and external weights. The ballast material may be selected andarranged in the base 101 so that the base 101 may float horizontally.Accordingly, even though the marine data acquisition node 100 may bedeployed at a slope or ridge of water bottom 180, the ballast materialmay allow the base 101 to float horizontally rather than aligning to awater bottom slope (e.g., seafloor slope) as a marine data acquisitionnode positioned directly on the water bottom 180 may.

Each of arms 102, 104, 106, and 108 may be coupled to, or otherwiseprotrude from, base 101 by any means suitable, such as, for example,welds, screws, bolts, and/or other techniques known in the art. Each ofthe arms 102, 104, 106, and 108 may be made, for example, from a rigid,high strength, high density plastic or another rigid, high strengthmaterial suitable for subsea deployment. Additionally, each of the arms102, 104, 106, and 108 may be constructed from an electricallynon-conducting material.

Each of the arms 102, 104, 106, and 108 may be generally tubal in shape.For example, each of the arms 102, 104, 106, and 108 may each resemble astraight conduit, such as a straight pipe or tube, and include two ends,for example: a proximal end 111 and a distal end 113. The proximal end111 of each arm 102, 104, 106, and 108 may be coupled to the lateralsurface of base 101, such that each arm 102, 104, 106, and 108 forms a90 degree angle with the lateral surface of the base 101, and extendslongitudinally away from the base 101, as illustrated in FIG. 1.Alternatively, each angle may be about 30 degrees, about 45 degrees, orabout 60 degrees from vertical. However, it should be understood thatangles with measurements, i.e. degrees, other than the above statedmeasurements, may also be used in particular applications. Each arm 102,104, 106, and 108 may be coupled to the base 101 at the same angle aseach of the other arms or at a different angle than each of the otherarms (staggered angles).

Each of the arms 102, 104, 106, and 108 may have a circularcross-section, or the cross-section may be, without limitation,triangular, square, pentagonal, hexagonal, or any combination thereof.Each of the arms 102, 104, 106, and 108 may have a differentcross-sectional shape than the other arms (staggered cross-sectionalshapes), or the cross sectional shape may be the same for all of thearms 102, 104, 106, and 108. Each of the arms 102, 104, 106, and 108 maydefine a longitudinally oriented interior chamber (not shown) thatextends along the length of each of the arms 102, 104, 106, and 108, andmay be closed at both ends, for example. Each of the arms 102, 104, 106,and 108 may have a length, for example, of about 1-25 meters, about 1meter to about 4 meters, about 4 meters to about 7 meters, about 7meters to about 10 meters, about 10 meters to about 13 meters, about 13meters to about 16 meters, about 16 meters to about 19 meters, or about22 meters to about 25 meters. However, it should be understood thatranges for lengths other than the above stated ranges, may also be usedin particular applications. The arms 102, 104, 106, and 108 may have adiameter, for example of about 5 centimeters to about 50 centimeters orabout 10 centimeters to about 20 centimeters. However, it should beunderstood that ranges for diameters other than the above stated ranges,may also be used in particular applications. Also, each of arms 102,104, 106, and 108 may have the same diameters and/or lengths as each ofthe other arms, or different diameters (staggered diameters) and/orlengths (staggered lengths) than each of the other arms.

The arms 102, 104, 106, and 108 may each include at least onegeophysical sensor, such as receiver electrodes 114, 116, 118, and 120.The receiver electrodes 114, 116, 118, and 120 may be used for electricfield measurement. By way of example, the receiver electrodes 114, 116,118, and 120 may measure one or more components of the energy field. Theenergy field may be an electromagnetic field. Each of the receiverelectrodes 114, 116, 118, and 120 may be mounted in the distal end 113of each of the arms 102, 104, 106, and 108. Alternatively, the receiverelectrodes 114, 116, 118, and 120 may be mounted along the length (fromand including the proximal end 111 to and including the distal end 113)of each of the arms 102, 104, 106, and 108, and have a longitudinalseparation, for example, of about 1 meter, about 3 meters, about 5meters, about 7 meters, or about 10 meters. However, it should beunderstood that ranges for longitudinal separation other than the abovestated ranges, may also be used in particular applications. Also, aswould be understood by one of ordinary skill in the art with the benefitof this disclosure, a greater separation between the electrodes mayenhance the ability to detect electric field data; thus, location of thereceiver electrodes 114, 116, 118, and 120 at or near the distal end 113of each of the arms 102, 104, 106, and 108 may be desirable.Additionally, the longitudinal separation for a particular one of thereceiver electrodes 114, 116, 118, and 120 on a corresponding one of thearms 102, 104, 106, and 108 may have the same longitudinal separation aseach receiver electrode on the other arms or may have differentlongitudinal separation than the other receiver electrodes 114, 116,118, and 120 on the other arms 102, 104, 106, and 108 (staggeredseparation).

The receiver electrodes 114, 116, 118, and 120 may be configured to bein contact with water when the first marine data acquisition node 100 isdeployed in the body of water 170. Without limitation, the receiverelectrodes 114, 116, 118, and 120 may be configured to detect changes inan energy field due to the interaction with a subsurface rock formation,such as one or more parameters related to the energy field (e.g.,voltage). The receiver electrodes 114, 116, 118, and 120 may be any of avariety of electrodes suitable for use in marine EM surveying,including, for example, silver-silver chloride electrodes. Electricalconductors (not shown) extending between the receiver electrodes 114,116, 118, 120 and sensor electronics 110 may electrically connect thereceiver electrodes 114, 116, 118, and 120 with the sensor electronics110 via the longitudinally oriented interior chamber (not shown) of eachof the arms 102, 104, 106, and 108, as mentioned previously.

As illustrated in FIG. 1, first marine data acquisition node 100 mayinclude at least one weight 130 configured to anchor first marine dataacquisition node 100 to the water bottom 180. Additionally, the weight130 may include a pressure sensor to measure depth and position inrelation to a marine data acquisition node. The weight 130 may befabricated out of materials, such as, for example, stainless steel,galvanized steel, titanium, metal alloys, or any combination thereof.The weight 130 may be hydrodynamically shaped, such as, for example,oval shaped, oblong shaped, or rocket shaped. Weight 130 may be coupledto base 101 by way of line 154. The line 154 may include, for example,rope, chain, wire, nylon, or other suitable anchor lines.

Line 154 may have a certain length, for example, a line length betweenabout 1 meter and about 100 meters, such that the base 101 of firstmarine data acquisition node 100, once deployed, may hover at a constantdistance above water bottom 180, or a constant distance from the watersurface 134. Other ranges for line lengths may include about 1 meter toabout 50 meters, about 50 meters to about 100 meters, about 100 metersto about 150 meters, about 150 meters to about 200 meters, about 200meters to about 250 meters, or about 250 to about 300 meters. However,it should be understood that ranges for line lengths other than theabove stated ranges, may also be used in particular applications. Arelease mechanism 155 to release the first marine data acquisition node100 may be provided at one or more locations along the line 154. Releasemechanism 155 may include any suitable mechanism for decoupling the line154 between the weight 130 and the base 101, including, withoutlimitation, a burn wire or a releasable latch, among others. The releasemechanism 155 may be operated, for example, by sensor electronics 110.Where the release mechanism 155 may include a burn wire, for example, aconstant current (e.g., 1.60±0.05 amps) may be applied, when activatedby sensor electronics 110, to heat burn wire, such that burn wire issevered, thereby releasing the first marine data acquisition node 100.The length of the burn wire may be the same or different than the lengthof the line 154. Additionally, a plurality of release mechanisms 155(e.g., burn wires, releasable latches, etc.) may be provided along theline 154 at different locations to allow for release of the first marinedata acquisition node 100, for example, in the event that lower portionsof the lines are stuck. Where there is a plurality of release mechanisms155 coupled to the line 154, at least one burn release mechanism 155among the plurality of release mechanisms 155 may be coupled to the line154 at a location that may be higher than a location of the water bottom180 and/or seafloor debris. This arrangement may provide severaladvantages and properties to the first marine data acquisition node 100,such as, for example, the first marine data acquisition node 100 may beless likely to get stuck in seafloor stones and/or debris than a marinedata acquisition node positioned directly on the water bottom 180, andthe line 154 coupling the weight 130 including a number of releasemechanisms 155 may facilitate returning the first marine dataacquisition node 100 to the water surface 134. Also, the base 101 offirst marine data acquisition node 100 hovering at a distance above thewater bottom 180 may result in the acquired electromagnetic and/orseismic data being less sensitive to local variations in the waterbottom 180 than a marine data acquisition node positioned directly onthe water bottom 180. For first marine data acquisition node 100, thearms 102, 104, 106, and 108 may be free in the body of water 170 asopposed to previous approaches that included a marine data acquisitionnode positioned on the water bottom 180. This may reduce, mitigate,and/or eliminate bending of the arms 102, 104, 106, and 108 that mayresult from contact with water bottom 180 objects, such as stones and/ordebris if the arms 102, 104, 106, and 108 were placed on the waterbottom 180.

Referring now to FIG. 2 a, an embodiment of first marine dataacquisition node 100 is illustrated that uses a plurality of weights,for example, weights 122, 124, 126, 128 and 130, configured to anchorfirst marine data acquisition node 100 to the water bottom 180. Each ofthe weights 122, 124, 126, 128 and 130 may be coupled to base 101 by wayof lines 146, 148, 150, 152, and 154, respectively. Each line may have acertain length, for example, a length between 1 and 100 meters, suchthat the base 101 of first marine data acquisition node 100, oncedeployed, may hover at a constant distance above the water bottom 180,or a constant distance from the water surface 134. Additionally, base101 may move from a first distance above water bottom 180 to a seconddistance above water bottom 180 after the marine data acquisition node100 is deployed. As previously described, embodiments may furtherinclude release mechanisms 155 (e.g., shown on FIG. 1) or other suitablerelease point to release the first marine data acquisition node 100 atone or more locations along the lines 146, 148, 150, 152, 154.

The base 101 may include at least one retractable device, for example,such as spools 136, 138, 140, 142 and 144. Each of the lines 146, 148,150, 152, and 154 may be reeled on each of the spools 136, 138, 140,142, and 144, respectively.

As illustrated in FIG. 2B, each of the spools 136, 138, 140, 142, and144 may extend each of the lines 146, 148, 150, 152, and 154,respectively, as each of the spools spins in one direction.Alternatively, each of the spools 136, 138, 140, 142, and 144 mayretract each of the lines 146, 148, 150, 152, and 154, respectively, aseach spool spins in the opposite direction. For example,counterclockwise spinning may shorten each line, while clockwisespinning may lengthen each line. Alternatively, clockwise spinning mayshorten each line, while counterclockwise spinning may lengthen eachline. The plurality of lines 146, 148, 150, 152, and 154 may be adjustedso that the marine data acquisition node 100 is level.

Referring to FIGS. 2A and 2B, each of the spools 136, 138, 140, 142, and144 may be mounted on the lateral surface of the base 101, such as, forexample, each of the spools 136, 138, 140, 142 may be mounted near abottom portion of each of the lateral faces of the base 101, such that,when the lines 146, 148, 150, 152, are completely retracted, the weights122, 124, 126, 128 abut portions of the lateral surface of the base 101,such as, for example, portions of the bottom corners of the base 101(e.g., wherein the base 101 is cube shaped). Spool 144 may be mounted onthe center of the bottom side (seafloor facing side) of base 101, suchthat weight 130 abuts the center of the bottom side (seafloor facingside) of base 101, where line 154 is completely retracted. Where line154 is extended, weight 130 may anchor first marine data acquisitionnode 100 to the water bottom 132. Techniques for mounting the spools136, 138, 140, 142, and 144 to the base 101 may include any suitabletechnique known in the art, such as, for example, bolting, screwing,welding, and/or other techniques known in the art. It should beunderstood that spools 136, 138, 140, 142 are merely examples and thatother suitable retractable devices may be used on base 101 to retrieveand/or extend lines 146, 148, 150, 152, and 154. For example, anysuitable device may be use to adjust the distance of the base 101 abovethe water bottom 132. In some embodiments, after deployment, thedistance of the base 101 above the water bottom 132 may be adjusted, forexample, the base 101 may be moved from a first distance above the waterbottom 132 to a second distance above the water bottom 132. The firstdistance may be greater, or less, than the second distance, depending onwhether it is desired to increase or decrease the distance of the base101 from the water bottom 132.

Each of the weights 122, 124, 126, 128 and 130 may be deployable. Eachspool may be motorized, thereby allowing winding and unwinding of eachline. Also, the weights 122, 124, 126, 128 and 130 may be ejected frombase 101. In order to eject the weights 122, 124, 126, 128 and 130laterally away from the base 101 with significant force, e.g., a forcesufficient to place the weights 122, 124, 126, 128 and 130 at desiredlocations along the water bottom 180, each of the spools 136, 138, 140,142, and 144 may include a jettison system that may eject the weights122, 124, 126, 128 and 130 through the body of water 170 and to thewater bottom 180. Sensor electronics 110 may be electrically coupled,via wires (not shown), to each of the spools 136, 138, 140, 142, and144, enabling activation of the motorized spools and the jettisonsystem. During activation, the spools 136, 138, 140, 142, and 144 maywind (retract and/or tighten) the corresponding lines 146, 148, 150,152, and 154, thus, recovering the weights 122, 124, 126, 128 and 130and/or stabilizing (via tightening of the line) the weights 122, 124,126, 128 and 130 against drifting due to subsea conditions, such as, forexample, ocean currents. The spools 136, 138, 140, 142, and 144 may alsounwind (extend) the lines 146, 148, 150, 152, and 154 and/or jettisonthe weights 122, 124, 126, 128 and 130, thus, deploying the weights 122,124, 126, 128 and 130 toward the water bottom 180. FIG. 2C illustratesweights 122, 124, 126, 128 and 130 deployed, and, thus, anchoring firstmarine data acquisition node 100 to the water bottom 180. Afterdeployment, the lines 146, 148, 150, 152, and 154 may be tightened tostabilize the position of first marine data acquisition node 100. Lines146, 148, 150, 152, and 154 may also include receiver electrodes 156,158, 160, 162 and 164, respectively. Each of the receiver electrodes156, 158, 160, 162 and 164 may be embedded within their respective lines146, 148, 150, 152, and 154. Electrical wires (not shown) within thelines 146, 148, 150, 152, and 154 may provide for an electricalconnection to sensor electronics 110.

As illustrated in FIG. 3, embodiments may include a first marine dataacquisition node 100 and a second marine data acquisition node 200. Insome embodiments, one or more receiver electrodes 115, 117 and 215, 217may be attached to and/or integrated within each of the lines 154, 254,respectively. Lines 154, 254 may couple weights 130, 230 to the firstmarine data acquisition node 100 and a second marine data acquisitionnode 200, respectively. Receiver electrodes 115, 117 and 215, 217 may beconfigured to transfer data to the sensor electronics 110, 210 of firstmarine data acquisition node 100 and second marine data acquisition node200, respectively, via electrical conductors (not shown), such as, forexample, wires. As illustrated, lines 154, 254 may be orientedvertically and, thus, receiver electrodes 115, 117 and 215, 217 may alsobe oriented vertically, allowing for measurement of a vertical componentof the electric field. The spacing of receiver electrodes 115, 117 and215, 217 on the corresponding lines 154, 254 may be substantiallylonger, for example, up to 100 meters or more, than the arms 102, 104,106, and 108 of the first marine data acquisition node 100 and the arms202, 204, 206, and 208 of the second marine data acquisition node 200,which may be on the order of tens of meters. This may reduce, mitigate,and/or eliminate movement noise associated with the measurement.

As illustrated in FIG. 3, first marine data acquisition node 100 mayinclude base 101, and second marine data acquisition node 200 mayinclude base 201, in accordance with example embodiments. Weight 130 mayanchor first marine data acquisition node 100 to the water bottom 180via line 154. Weight 230 may anchor second marine data acquisition node200 to the water bottom 180 via line 254. Each of the lines 154, 254 maybe of different lengths and/or may be of adjustable lengths in order toposition the first and second marine data acquisition nodes 100, 200 inrelation to the water bottom 180 to counter bathymetry variations, forexample. The length of one or more lines, such as, for example, lines154, 254, associated with the first and second marine data acquisitionnodes 100, 200, may be adjusted by spools 144, 255 disposed on thecorresponding base 101, 201 or coupled thereto. Techniques for couplingthe spools 144, 255 to the base 101, 201 of the first and second marinedata acquisition node 100, 200 may include any suitable technique knownin the art, such as, for example, bolting, screwing, welding, and/orother techniques known in the art. Where first marine data acquisitionnode 100 is provided with a spool 144, the spool 144 may be actuated sothat the first marine data acquisition node 100 may be raised andlowered during a marine geophysical survey to acquire data at differentdepths. The spool 144 may shorten or lengthen line 154.

In some embodiments, the first marine data acquisition node 100 and thesecond data acquisition node 200 may be connected together with a firstline 119 and/or a second line 121 in order to enable a longer dipole tobe created if the electric field is measured between the first marinedata acquisition node 100 and the second data acquisition node 200, withthe first line 119 and/or second line 121 as a reference. While FIG. 3illustrates use of first line 119 and second line 121, it should beunderstood that first line 119 and second line 121 may be usedindependent of one another to couple the first marine data acquisitionnode 100 and the second marine data acquisition node 200 to one another.First line 119 and/or second line 121 may each comprise high-strengthwire or a wire strengthened with a rope or a cable assembly having wireand strength members. First line 119 is suspended between dataacquisition node 100 and second data acquisition node 200 such that allor part of first line 119 is not in contact with water bottom 180.Second line 121 may extend along the water bottom 180. The first line119 and/or the second line 121 may be coupled to base 101 and base 201.Alternatively, more than two marine data acquisition nodes may beconnected by multiple lines and may form a mesh-like connection betweenthe marine data acquisition nodes in order to map the potential(voltage) differences of the electric field (at least two points) in thearea where the marine data acquisition nodes have been deployed, suchas, on the water bottom 180, for example. The voltage readings may beturned into a voltage map of the area where the marine data acquisitionnodes have been deployed. Differences, such as, distances betweenmultiple marine data acquisition nodes may be used to estimate theelectric field. Also, multiple voltage points may be used to calculate aderivative which may allow avoiding noise or outliers. In someembodiments, when the first marine data acquisition node 100 and thesecond marine data acquisition node 200 may be released to be returnedto the sea surface (e.g. water surface 134 on FIG. 1), the first line119 and/or second line 121 between the first marine data acquisitionnode 100 and the second marine data acquisition node 200 may alsodisconnect at one or more predetermined points to simplify retrieval ofthe first and second marine data acquisition nodes 100, 200 and/or toreduce, mitigate, and/or eliminate tangle among the first and secondmarine data acquisition nodes 100, 200 as they travel through the bodyof water 170 to the water surface 134.

FIG. 4 illustrates a marine geophysical survey system 166 that includesa first marine data acquisition node 100 and a second marine dataacquisition node 200 in accordance with example embodiments. The marinegeophysical survey system 166 includes a survey vessel 168 that movesalong the surface of the body of water 170. The survey vessel 168generally may include equipment, shown generally at 172 and collectivelyreferred to herein as “survey equipment.” The survey equipment 172 mayinclude devices (none shown separately) for determining geodeticposition of the survey vessel 168 (e.g., a global positioning systemsatellite receiver signal) and actuating an energy source 174 (explainedfurther below) at selected times, among others. A submersible vehicle176 carrying the energy source 174 may be attached to the survey vessel168 by cable 178. The marine geophysical survey system 166 may alsoinclude a towed energy source 174 without the assistance of asubmersible vehicle 176. Alternatively, marine geophysical survey system166 may include a submersible vehicle 176 which acts as a remotelyoperated vehicle (ROV), without the use of cable 178.

As illustrated, one or more marine data acquisition nodes, such as firstmarine data acquisition node 100 and second marine data acquisition node200 may be located near the water bottom 180, but not directly on thewater bottom 180. Although FIG. 4 illustrates first and second marinedata acquisition nodes 100, 200 and one energy source 174, it is to beunderstood that the number of devices is not a limitation on the scopeof the disclosure. First marine data acquisition node 100 may be coupledto weight 130 via line 154. Second marine data acquisition node 200 maybe coupled to weight 230 via line 254. Other configurations may includemore or fewer than the first and second marine data acquisition nodes100, 200 and energy source 174. For example, embodiments may includedeployment of a plurality of the marine data acquisition nodes 100, 200near the water bottom 180 wherein the plurality of the marine dataacquisition nodes 100, 200 are configured the same.

In operation, the energy source 174 may emit an energy field into thebody of water 170 that interacts with subterranean formations 182 belowthe water bottom 180. Without limitation, the first and second marinedata acquisition nodes 100, 200 may detect changes in the energy fielddue to the interaction with the subterranean formations 182 and generateresponse signals which may then be recorded for later analysis. When themarine geophysical survey is complete or at another desired time, theburn wires 184, 186 may burn (burn wires 184, 186 may be embedded inlines 154, 254, respectively) allowing the first and second marine dataacquisition nodes 100, 200 to float to the water surface 134 forrecovery. After recovery, the data stored in each of the first andsecond marine data acquisition nodes 100, 200 may be analyzed to infercertain properties of the subterranean formations 182.

In some embodiments, a geophysical data product may be manufactured frommeasurements of one or more components of the energy field made with themarine data acquisition node 100. The geophysical data product may berecorded on one or more non-transitory computer readable media suitablefor importing onshore. The imported geophysical data product may befurther processed or analyzed via a geophysical analysis.

Although specific systems and methods have been described above, thesesystems and methods are not intended to limit the scope of the presentdisclosure, even where only a single system or method is described withrespect to a particular feature. Examples of features provided in thedisclosure are intended to be illustrative rather than restrictiveunless stated otherwise. The above description is intended to cover suchalternatives, modifications, and equivalents as would be apparent to aperson skilled in the art having the benefit of this disclosure.

The scope of the present disclosure includes any feature or combinationof features disclosed herein (either explicitly or implicitly), or anygeneralization thereof, whether or not it mitigates any or all of theproblems addressed herein. Various advantages of the present disclosurehave been described herein, but systems and methods disclosed herein mayprovide some, all, or none of such advantages, or may provide otheradvantages.

Therefore, the present disclosure is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular systems and methods disclosed above are illustrative only, asthe present disclosure may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Although individual systems and methodsare discussed, the invention covers all combinations of all thosesystems and methods. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particularillustrative systems and methods disclosed above may be altered ormodified and all such variations are considered within the scope andspirit of the present invention. All numbers and ranges disclosed abovemay vary by some amount. Whenever a numerical range with a lower limitand an upper limit is disclosed, any number and any included rangefalling within the range are specifically disclosed. Moreover, theindefinite articles “a” or “an,” as used in the claims, are definedherein to mean one or more than one of the element that it introduces.Also, the terms in the claims have their plain, ordinary meaning unlessotherwise explicitly and clearly defined by the patentee. If there isany conflict in the usages of a word or term in this specification andone or more patent or other documents that may be incorporated herein byreference, the definitions that are consistent with this specificationshould be adopted for the purposes of understanding this disclosure.

What is claimed is:
 1. A marine data acquisition node, comprising: abase having a buoyancy such that the base is configured to float in abody of water; a seismic sensor coupled to the base; a weight configuredto anchor the base to a water bottom; and a line connected between theweight and the base configured to prevent the base from floating to asurface of the body of water.
 2. The marine data acquisition node ofclaim 1 wherein the seismic sensor is a hydrophone, geophone, particlevelocity sensor, particle displacement sensor, particle accelerationsensor, or pressure gradient sensor.
 3. The marine data acquisition nodeof claim 1 further comprising an arm coupled to the base, wherein thearm comprises a receiver electrode configured for contact with water. 4.The marine data acquisition node of claim 3 further comprising sensorelectronics disposed within the base and electrically coupled to thereceiver electrode.
 5. The marine data acquisition node of claim 1further comprising a buoyant material coupled to the base.
 6. The marinedata acquisition node of claim 1, wherein the base is configured tofloat above the water bottom.
 7. The marine data acquisition node ofclaim 1 further comprising a release mechanism coupled to the line. 8.The marine data acquisition node of claim 1 further comprising a ballastmaterial disposed within the base.
 9. The marine data acquisition nodeof claim 1 further comprising a spool coupled to the base, wherein theline is at least partially wound on the spool.
 10. The marine dataacquisition node of claim 1 further comprising a plurality of spoolscoupled to the base and a plurality of weights coupled to the pluralityof spools.
 11. A marine data acquisition system, comprising: a pluralityof marine data acquisition nodes, wherein the marine data acquisitionnodes each comprise: a base having a buoyancy such that the base isconfigured to float in a body of water; a geophysical sensor coupled tothe base; a weight configured to anchor the base to a water bottom; anda line connected between the weight and the base configured to preventthe base from floating to a surface of the body of water.
 12. The marinedata acquisition system of claim 11, wherein the geophysical sensorcomprises a seismic sensor.
 13. The marine data acquisition system ofclaim 11, wherein the plurality of marine data acquisition nodes arepositioned in a body of water such the base of each of the marine dataacquisition nodes floats above the water bottom.
 14. The marine dataacquisition system of claim 13, further comprising a line coupling twoof the marine data acquisition nodes to one another.
 15. The marine dataacquisition system of claim 11, further comprising an energy source. 16.A marine survey method, comprising: deploying a marine data acquisitionnode in a body of water, wherein the marine data acquisition nodecomprises: a base having a buoyancy such that the base floats in thebody of water; a geophysical sensor coupled to the base; a weight thatanchors the marine data acquisition node to a water bottom; and a lineconnected between the weight and the base that prevents the base fromfloating to a surface of the body of water; and generating signals withthe geophysical sensor in response to energy emitted from an energysource, wherein the signals can be used to infer properties of asubsurface formation.
 17. The method of claim 16, wherein thegeophysical sensor comprises a seismic sensor.
 18. The method of claim16 further comprising recovering the marine data acquisition node fromthe body of water.
 19. The method of claim 16, wherein the recoveringcomprises decoupling the line between the weight and the base.
 20. Themethod of claim 16, wherein the deploying comprises extending the linefrom the base such that the weight extends away from the base.
 21. Themethod of claim 16 further comprising moving the base from a firstdistance above the water bottom to a second distance above the waterbottom after the deploying of the marine data acquisition node in thebody of water.
 22. The method of claim 16, wherein the deployingcomprises extending a plurality of lines from the base.
 23. The methodof claim 16 further comprising adjusting the plurality of lines so thatthe marine data acquisition node is level.
 24. The method of claim 16further comprising deploying more than one of the marine dataacquisition node.
 25. A method of manufacturing a geophysical dataproduct, comprising: deploying a marine data acquisition node in a bodyof water, wherein the marine data acquisition node comprises: a basehaving a buoyancy to float in the body of water; a geophysical sensorcoupled to the base; a weight that anchors the marine data acquisitionnode to a water bottom; and a line; generating signals with thegeophysical sensor in response to energy emitted from an energy source,wherein the signals can be used to infer properties of a subsurfaceformation; and recording the signals on one or more non-transitorycomputer readable media, thereby creating the geophysical data product.26. The method of claim 25 further comprising importing the geophysicaldata product onshore and performing further data processing orgeophysical analysis on the geophysical data product.
 27. The method ofclaim 26 wherein the geophysical sensor comprises a seismic sensor. 28.The method of claim 25 further comprising recovering the marine dataacquisition node from the body of water, wherein the recoveringcomprises activating a release mechanism to release the base from theweight.
 29. The method of claim 25 wherein the deploying comprisesextending the line toward the water bottom.